The present invention relates to a magnetic head loading/unloading apparatus used in a disk apparatus, and more particularly to a magnetic head loading/unloading apparatus having a head arm on one end of which is mounted a magnetic head, the head arm being driven by a magnetic force generated by a coil.
Generally, a magneto-optical disk apparatus uses an optical-modulation recording method. In this method, when previously recorded information on a magneto-optical disk is rewritten, an erasing operation in which directions of magnetization formed on the magneto-optical disk are uniformly changed to an erasing direction is performed first, and then a direction of magnetization of a magnetic head is switched to a recording direction. Thereafter, a laser beam is projected on the magneto-optical disk to perform a recording operation of data. Accordingly, in the above-mentioned recording method, time is spent on performing the erasing operation, and thus there is a problem in that time spent on the recording operation is increased.
On the other hand, there is a magnetic-modulation recording method in which an over-writing is enabled. The magnetic-modulation recording method not only improves a recording-data transfer rate but also is effective in a mark-edge recording method which is used for increasing recording density.
A description will now be given, with reference to FIGS.1 through 4, of a magneto-optical disk apparatus using a magnetic-modulation recording method.
As shown in FIGS.1 through 4, a magneto-optical disk 1 has a spirally formed tacking guiding groove, a recording surface of the disk being a bottom surface. A magnetic head 2 for generating a magnetic field sufficient for recording and erasing information on the magneto-optical disk 1 is mounted on an end of a head arm 3 formed of a leaf spring. A carriage 4 is slidable in a tracking direction underneath the magneto-optical disk 1 so that a top surface of the carriage 4 faces the bottom surface of the magneto-optical disk 1.
A fixed optical unit 5 has a laser diode, a light receiving element and other optical parts not shown in the figures. The magneto-optical disk 1 is loaded on a main body 7 in a state where the magneto-optical disk 1 is accommodated in a cartridge 6. A recording of information on the magneto-optical disk 1 and/or a reproducing of information from the magneto-optical disk 1 is performed by means of a laser beam projected through an objective lens 8 and by means of a magnetic field generated by the magnetic head 2.
That is, a laser beam 9 emitted by the fixed optical unit 5 passes through the objective lens 8, as shown in FIG.4, after its direction is bent 90 degrees by a reflection mirror 16 provided on the carriage 4. Thereafter, the laser beam 9 is converged on a recording film 19 of the magneto-optical disk 1.
The objective lens 8 is moved by an actuator 15 in a direction X parallel to and a direction Y perpendicular to the recording surface of the magneto-optical disk 1. The objective lens 8 is moved so that an appropriate laser-beam spot 17 is formed even if a fluctuation of a rotational plane and eccentricity of a rotation are generated in association with a rotation of the magneto-optical disk 1.
The head arm 3 is supported on the carriage 4 via a first connecting member 11 and a second connecting member 12. Accordingly, the magnetic head 2 provided above the magneto-optical disk 1 is always positioned opposite to the laser beam spot 17 relative to the magneto-optical disk 1.
The magnetic head 2 has such a shape that the magnetic head 2 receives a lifting force in the direction Y due to an air flow in a tangential direction generated by a high-speed rotation of the magneto-optical disk 1, and thus the magnetic head 2 is maintained in a state in which the magnetic head 2 floats on the magneto-optical disk 1.
The first connecting member 11 is rotatably connected to the second connecting member 12 via a pin 10. The first connecting member 11 is rotated by a driving mechanism (not shown in the figures) so that the magnetic head 2 on an end of the head arm 3 is moved to a load position in which the magnetic head 2 is very close to the magneto-optical disk 1 or to an unload position in which the magnetic head 2 is distant from the magneto-optical disk 1.
When the cartridge 6 accommodating the magneto-optical disk 1 is loaded in the main body 7, a shutter 6b provided on the cartridge 6 is opened, and the magneto-optical disk 1 is place on a turntable 14. At the time the cartridge 6 is loaded into the main body 7, the magnetic head 2 is lifted to the unload position as shown in FIG. 3 so as to prevent the head 2 from colliding with the cartridge 6.
After the magneto-optical disk 1 is placed on the turntable 14, the turntable 14 is rotated by a spindle motor 13, and thus the magneto-optical disk 1 is rotated at a predetermined speed. The laser beam 9 emitted by the fixed optical unit 5 is then projected on the magneto-optical disk 1.
Thereafter, as shown in FIG.2, the first connecting member 11 is rotated downwardly about the pin 10 on the second connecting member 12, and thus the magnetic head 2 is moved down to the load position close to the magneto-optical disk 1. In this state, since the magneto-optical disk 1 is rotated at the predetermined speed, an air flow is formed near the surface of the magneto-optical disk 1 due to viscosity of the air. Accordingly, the magnetic head 2 positioned close to the magneto-optical disk 1 receives a lifting force in the Y direction generated by the air flow, and thus the magnetic head 2 floats on the magneto-optical disk 1.
It should be noted that the head arm 3 has an elastic property, and as an elastic force of the head arm 3 balances the lifting force of the head 2, the magnetic head 2 floats a few micron millimeters above the magneto-optical disk 1. The magnetic head 2 then applies a modulated magnetic field on the magneto-optical disk 1, and the recording film 19 is partially heated above the curie point by converging the laser beam 9 which is not modulated on the recording film 19. The recording film 19 of which the temperature exceeds the curie point looses a magnetic coercive force, and thus is magnetized by the magnetic field applied by the magnetic head 2.
After a recording/reproducing operation is ended, the rotation of the turntable 14 by the spindle motor 13 is stopped. When the rotational speed of the magneto-optical disk 1 is reduced, the magnetic head 2 may collide with the magneto-optical disk 1 because the lifting force exerted on the magnetic head 2 is reduced.
In order to avoid this situation, the magnetic head 2 is lifted up to the unload position which is distant from the magneto-optical disk 1. This movement of the magnetic head 2 is performed by rotating the first connecting member 11 upwardly about the pin 10 on the second connecting member 12. Thereafter, the rotation of the spindle motor 13 is stopped, and then the cartridge 6 is ejected while the magnetic head 2 is lifted
However, in the above-mentioned magneto-optical disk apparatus, in order to prevent the second connecting member 12 colliding with the cartridge 6 when the magnetic head 2 is moved to the innermost side of the magneto-optical disk, it is necessary to lengthen a distance between the magnetic head 2 and the second connecting member 12. Additionally, when the head arm 3 and the first connecting member 11 are rotated upwardly, in order to avoid a permanent deformation of the head arm 3, the length of the head arm 3 must be lengthened, and accordingly a large driving mechanism is needed for driving the first connecting member 11 due to the large weight of the head arm 3. Therefore, there is a problem in that an accessing speed of the magnetic head 2 mounted on an end of the head arm 3 is reduced. Additionally, the above-mentioned conventional apparatus has a complicated structure, and thus assembly takes time and labor, which condition results in an increase in manufacturing costs.
Other than the above-mentioned magneto-optical disk apparatus, an apparatus disclosed in Japanese Laid-Open Patent Application No. 3-104069 has been proposed in which apparatus a lamination type piezoelectric actuator is used. In this apparatus, the head arm is rotated by a displacement amplifying mechanism driven by the lamination type piezoelectric actuator.
However, in this construction, a current must be supplied continuously to the actuator while maintaining the magnetic head in the load position, and thus there is a problem that an internal temperature of the apparatus increases due to a large consumption of electric power. Another problem is that when a power source is unintentionally cut off due to, for example, a power failure, it is difficult to maintain the magnetic head in the unload position.